Born from a violent revolution, the U.S. constitution ensures that gun ownership is a fundamental right. Today, there are more than 7.5 million gun stores in the United States, and 29.1% of American adults own at least one firearm of some kind. While the second amendment grants U.S. citizens the right to own guns, federal laws also restrict certain people from buying firearms.

All states have to abide by federal laws surrounding gun ownership, but these laws are limited and each state can expand or further limit these laws. Though no state has especially strict gun laws compared to many other European and high income nations, some come close. To determine the states where it is hardest to buy a gun, 24/7 Wall St. reviewed state gun laws to identify states with the most restrictive laws such as universal background checks and licensing requirements.

Federal regulations require individuals to meet certain criteria before they can purchase a firearm from a licensed dealer. Licensed dealers are required to conduct background checks on gun buyers and are not allowed to sell firearms to anyone who is a fugitive from law, has been declared mentally “defective” to the extent that he or she is incapable of managing his or her own affairs, is an illegal alien, or has been convicted of misdemeanor offense of domestic violence.

However, background checks are not required by federal law for firearms purchased from private sellers, a technicality commonly referred to as the gun show loophole. To many, this loophole is especially problematic as private sales account for an estimated 40% of all gun sales nationwide.

Even before the San Bernardino mass shooting, which resulted in the deaths of 16 people, California’s gun laws were among the strictest in the nation. For example, whenever a firearm is sold or loaned in California, the dealer must submit an application to the Department of Justice in order to determine whether the buyer meets the state’s stringent background check criteria. Since the shooting, California Governor Jerry Brown signed new regulations into law, including background check requirements for ammunition purchases and a ban on large capacity magazines.

As is the case in most states with the strictest firearm regulations, California’s gun ownership rate of 20.1% of adults and the gun-related fatalities rate of 7.6 deaths per 100,000 people are relatively low compared to other states.

Due to the perceived inadequacy of federal regulations, some states have enacted uniquely comprehensive gun purchasing regulations. For example, 12 states, including many on this list, have addressed the gun show loophole, either by requiring a permit to purchase a gun, contingent upon the successful completion of a background check, or by requiring private sellers to contact local law enforcement to run a background check prior to the sale. An additional six states have effectively closed the gun show loophole for handgun purchases only.

While many states have enacted laws to ensure gun buyers undergo a background check, many also expanded on the federal government’s criteria. With the exception of Rhode Island, every state on this list prohibits anyone convicted of a gun-related misdemeanor from purchasing a firearm. In addition, the majority of states on this list restrict individuals who have been treated for alcohol or drug abuse from buying a gun.

A handful of states also take measures to ensure gun buyers are familiar with safe use and handling of a firearm. California, Connecticut, Maryland, Massachusetts, and Rhode Island all require some form of safety training or exam before an individual can obtain a license to buy any kind of firearm. Hawaii requires training only for handguns prior to purchase.

The connection between firearm regulations and gun-related death rates is controversial in the United States. However, it is indisputable that states with the strictest gun laws also tend to have fewer than average gun deaths. Except for Delaware, every state with the strictest gun purchasing laws has a lower firearm-related death rate than the national rate of 10.5 deaths per 100,000 people. Including Hawaii, the state with the fewest gun deaths per capita, six states on this list have a firearm death rates less than half the corresponding national rate.

To identify the hardest states to buy a gun, 24/7 Wall St. reviewed gun laws in each state as catalogued by the Law Center to Prevent Gun Violence. To compile our list, considered whether a state imposed: 1. universal background checks, 2. license requirements for handgun purchases, or 3. firearm purchasing limitations on at least four of the following five groups: individuals convicted of gun-related violent crimes, the dangerously mentally ill, drug abusers, alcohol abusers, and certain juvenile offenders. Only the states that met at least two out of the three qualifications made the list. Population figures came from the U.S. Census Bureau’s 2014 American Community Survey. Firearm-related deaths data came from the Centers for Disease Control and Prevention. Gun ownership rates for each state as of 2013 were obtained from a study published in 2015 from the Mailman School of Public Health at Columbia University.